This invention relates to the monitoring equipment for processing of liquids used in products for human consumption, e.g., dairy products such as milk, cream, and ice cream mix, other liquid food products, e.g., fruit juices and soups, or pharmaceuticals. The invention is more particularly concerned with an adapter and a technique for employing a standard thermometer or temperature gauge in sanitary conduits in which such liquid products are processed, and which permits the temperature gauge to be changed out or replaced when necessary, without incurring high material or labor costs and while maintaining sanitary conditions within the conduit.
Pasteurization is a process for heat treating milk or other food or ingestible product in order to kill pathogens such as bacteria or other microorganisms. The U.S. Public Health Service has published standards for equipment for the pasteurization of milk and other milk products, and there are similar regulations concerning equipment for processing other products. On the one hand, the temperature of the product has to be closely monitored at certain points in the process. This means that working thermometers or pressure gauges have to be present in the conduit, and must be replaced whenever they fail. On the other hand, in order to ensure that the sanitary conduit can be cleansed and sanitized between processes, the conduit is designed so that it can be completely cleaned of any milk or other product by washing it and rinsing it with a cleaning fluid that must reach every point on the interior of the conduit. No threaded connectors can be used anywhere that the liquid product flows, because of the difficulty in cleaning the threads.
Standard temperature gauges typically have a threaded stem that is used for securing the gauge into a threaded nipple in the associated equipment. A stainless steel temperature probe or finger then projects out of the threaded stem and into the conduit to which the threaded nipple is connected. Because these standard gauges rely on threaded connections to install them and hold them in place, an alternative technique has been employed for using thermometers and temperature gauges in pasteurizers or other sanitary conduits.
One technique that has been employed previously has been to install a flange disk over the stainless steel temperature probe, by welding it onto the finger or probe. Then, the flange disk can be secured to a sealing flange at an outer end of a tubular stub that connects to the conduit. A sanitary clamp, e.g., a so-called tri-clamp, compresses a sealing gland or ring between these two flanges, so there are no threads exposed to the product in the sanitary conduit. Unfortunately, these specially constructed gauges are many times more costly than the standard temperature gauges, and thus much more expensive to replace.
Another alternative is to employ a so-called thermometer well, which is a hollow finger that penetrates into the conduit, and allows the standard gauge to be installed with the finger or probe entering the hollow interior of the thermometer well. This does have the advantage of sanitary operation in that there are no exposed threads. However, the well itself has considerable thermal inertia, and this conceals any rapid temperature swings. That is, the probe itself is not in contact with the liquid, so detection of any temperature change is delayed. In some cases, where a specific temperature or a temperature differential is critical, failure to detect the temperature change can result in inefficient operation, or can produce undesirable changes in product quality, such as scalding.
In a regenerative heat exchanger of the type that is used in many pasteurizers, temperature differences between the raw product side and the pasteurized product side may be only a few degrees. For efficient operation it is important to monitor the temperatures there very closely.